Vehicle Friction Estimation Using Damper Force Sensors
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Solution Overview
Problem
Existing methods for estimating the coefficient of friction on roadways, such as those used in slip control systems and camera-based methods, are inaccurate and only provide values after the vehicle has passed the area, leading to inefficient vehicle dynamics control and potential safety issues.
Innovation Solution
A control device in a motor vehicle combines data from slip control and damper control systems to calculate a vehicle-independent coefficient of friction using actual wheel contact force and horizontal force, allowing for predictive estimation before reaching a surface area, and stores statistical coefficients of friction by subsurface class for improved accuracy and adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a slip control system is used to estimate the coefficient of friction, then the estimation is available after the vehicle has passed the area, but the accuracy is poor because vertical force is estimated by assuming even vehicle mass distribution
Solution Approach 1:
The patent introduces an intermediary system (damper control system with sensors) that directly measures vertical wheel contact forces. This intermediary measurement system provides accurate vertical force data to the coefficient of friction calculation, eliminating the need for inaccurate mass distribution assumptions while enabling real-time estimation before the vehicle reaches the assessment point.
Solution Approach 2:
The patent replaces the mechanical assumption-based estimation method (assuming even mass distribution) with a sensor-based measurement system. Force sensors in the damper control system directly measure vertical wheel contact forces, substituting the theoretical mechanical model with empirical mechanical measurement for superior accuracy.
2Loss of time
If camera-based methods are used to detect road surface conditions, then the estimation is available early, but the accuracy is poor because camera-based estimation is very imprecise
Solution Approach 1:
The patent replaces optical detection methods (camera-based estimation) with direct mechanical measurement using force sensors in the damper control system. This substitution provides accurate physical measurement of vertical wheel contact forces, eliminating the imprecision inherent in visual camera-based estimation while maintaining early availability of the data.
Solution Approach 2:
The patent introduces force sensors as an intermediary measurement device between the road surface and the control system. These sensors directly measure vertical wheel contact forces, providing an accurate physical intermediary that bridges the gap between road conditions and the coefficient of friction calculation, unlike the indirect optical methods.
3Adaptability or versatility
If statistical coefficients of friction are stored by subsurface class, then adaptability to different road conditions is improved, but device complexity increases due to additional data storage and processing
Solution Approach 1:
The patent segments the road surface data by subsurface class (different road surface types), storing statistical coefficients of friction separately for each class. This segmentation allows the system to adapt to different road conditions by selecting the appropriate statistical data, while organizing the complexity into manageable, categorized segments rather than a single undifferentiated data structure.
Solution Approach 2:
The patent performs preliminary classification of road surfaces into subsurface classes and pre-calculates statistical coefficients of friction for each class. This preliminary action organizes the data in advance, reducing the processing complexity during real-time operation as the system only needs to retrieve and apply the pre-computed statistical data for the identified surface class.
Data Source
AI summary
The invention relates to a method for estimating a friction coefficient (30) of a roadway (24) by means of a motor vehicle (10), wherein a control device (14) of the motor vehicle (10) receives, from a traction control system (17), a first estimated value of a maximum horizontal force (28) that can be transmitted to the roadway (24) by means of a wheel (11) of the motor vehicle (10). The invention provides that the control device (14) receives, from a damper controller (15), a second estimated value of a wheel contact-patch force (26) of the wheel (11), and calculates the friction coefficient (30) as a vehicle-independent friction coefficient (30) on the basis of the estimated values from the wheel contact-patch force (26) and the horizontal force (28).